The inventions described herein are useful in molding processes to locate pre-formed embedded fragments, obturators, aerodynamic boat tails and other desired components while manufacturing munitions. This utility has been developed using a 120 mm Projectile, an 81 mm Mortar, and a 40 mm grenade, but is not limited only to those specific warheads.
It is common for metal preformed fragments to be used in warheads. These fragments increase the lethal consistency of munitions by pre determining the size and mass of parts of the warhead. A polymer matrix can be used to keep such fragments in place during storage and launch. The polymer allows the energetic to accelerate the fragments with minimal effect on fragment velocities. The polymer is also used to position the fragments on the warhead.
There are challenges however in manufacturing using these approaches. Preformed fragments need a matrix material to envelop them to keep position and integrity during storage and launch. Polymer matrixes can be applied using low viscosity epoxies by pouring the material into a mold, but this process takes a significant amount of time to mix the epoxy, pour it into a mold cavity with the fragments, and allow it to cure. Warhead design may also require additional features that are problematic to existing processes. These include designs where fragments are not wanted in specific areas of the part. Old way to solve these problems included use of faster curing resin systems, and then use of post curing machining operations. A problem with the old ways was that two part resin systems can lead to errors in production due to incorrect mix ratios. This then requires many molds to increase production rate without actually improving cycle times. If a part is divided into multiple sections to be fabricated, it may require a process where material has to completely cure before adding in additional fragments and finishing the cycle. Post machining operations can also damage the polymer matrix and also increase cycle times. Obturators are often added then after processing as an extra step. Alternatively, celluloid material come in sheets that are not applicable as a matrix material with old ways. The celluloid in this form does not allow full embedding of the preformed fragments.